1. Field
The present disclosure relates to a lithium ion secondary battery.
2. Description of the Related Art
A lithium ion secondary battery can include a sulfide having good lithium ion conductivity as an inorganic solid electrolyte to provide a structure containing electrodes (a cathode and an anode) formed on two surfaces of a solid electrolyte layer and a current collector connected to each of the electrodes.
In the lithium ion secondary battery, graphite can be used as an anode active material since graphite is capable of intercalating and deintercalating lithium ions and may have a high capacity. Japanese Patent No. 2008-300148 is related to a lithium secondary battery having improved electrical conductivity by adhering particles of a transition metal that does not form an alloy with lithium on a surface of an anode active material that is formed of a carbonaceous material and using a polymer electrolyte as a solid electrolyte.
Japanese Patent No. 1999-310405 discloses graphite coated with a graphite or pitch for coating, and using the coated graphite as an anode of a lithium ion battery. Also, Japanese Patent No. 2012-049001 is related to an inorganic all-solid secondary battery including an anode active material formed of graphite and coated with amorphous carbon to decrease lithium ion conduction resistance of an anode.
Japanese Patent No. 2006-107812 is related to an inorganic solid electrolyte secondary battery that may have good battery characteristics by including a cathode, an anode, and an inorganic solid electrolyte, wherein the cathode includes a cathode active material layer and a cathode current collector layer, the anode includes an anode active material layer and an anode current collector layer, the cathode current collector layer and the anode current collector layer are a conductive metal oxide layer, and the anode active material layer is formed of a material having an operating voltage that is higher than 1.0 V vs. Li.
In order to detect a charge/discharge state of an inorganic all-solid secondary battery including a sulfide-based solid electrolyte, as disclosed in Japanese Patent No. 2005-285647, in a lithium ion battery, a pressure sensor overlaps the lithium ion battery, and a sandwiching member that sandwiches the lithium ion battery and the pressure sensor at both sides in an overlapped direction. Further, when the lithium secondary battery expands or contracts by charging/discharging of the battery, force loaded on the pressure sensor changes accordingly, and thus the volume change of the lithium ion battery is detected as an output value of the pressure sensor.
Japanese Patent No. 2006-012761 is related to a state estimation system of a secondary battery that includes a cathode and an anode, wherein each of the cathode and the anode are included in a case in a secondary battery. Further, a temperature sensor is disposed between restraining plates and thus is integrated with a secondary battery cell as one body. This temperature sensor is disposed in a manner to detect temperatures of the cathode and the anode with respect to at least one of the secondary batteries. An electronic control unit (ECU) outputs a state of charge (SOC) of the secondary battery according to a pressure detection value of the pressure sensor and a temperature detection value of the temperature sensor with consideration of a fact that volume change characteristics of electrodes change according to temperature change.
An overvoltage detection device disclosed in Japanese Patent No. 2006-269345 includes laminate, stacked in a thickness direction, covered batteries as lithium ion batteries, and pressure sensors that are inserted between laminate surfaces of the adjacent laminate covered batteries. Further, the pressure sensor measures a surface pressure (a contact pressure) applied on the laminate surface and determines whether overvoltage occurred in the laminate covered batteries by detecting whether the measured contact pressure is higher than a critical value or not.
Japanese Patent No. 2010-073544 is related to a battery unit including a solid battery, an accommodation case that accommodates the solid battery, a loading sensor installed on the accommodation case, and a sandwiching member that sandwiches the accommodation case and the loading sensor to detect accurate state of charge (SOC) of the battery unit.
Further, Japanese Patent No. 2013-065453 is related to a lithium ion battery capable of setting a discharge cut-off voltage, wherein a relationship between a potential of a cathode and a capacity of a cathode during discharging of the battery sets the discharge cut-off voltage, wherein each of a lithium nickel oxide and a lithium iron phosphate form a composite by reversible intercalation of lithium ions, and an anode potential at a time of discharge cut-off is a potential that does not cause changes in silicon oxide under the battery voltage.
However, since a lithium ion battery has a small difference between a redox potential of lithium and a redox potential of a graphite-lithium interlayer compound when graphite is used as an anode active material, lithium dendrites have been easily formed, and fast charging of the battery has been difficult. Further, since charge/discharge state of the lithium ion battery have been detected by changes in physical properties, such as pressure or temperature, of the battery, a device structure of the lithium ion battery has been complicated. Furthermore, the lithium secondary battery disclosed in Japanese Patent No. 2006-012761 may predict the potential of the anode from the relationship between the discharge potential of the cathode and the battery capacity, but a state of the anode may not be directly detected.